How to change timing of my mocap BVH and how to optimize keyframes
You can use the Simplify Curves addon, which is already with your Blender.


Enable the Addon;
Switch to Graph Editor, select all curves that you want to simplify, press Space and search for Simplify Curves. Then press F6 to tweak the Error theshold.






To be more accurate, you have to remove those unneeded "interpolated" keys manually, which needs time.